This invention relates to monitoring pilot flames in flare systems typically used in the oil and chemical industries. It particularly relates to the installation and the replacement of thermocouples in these systems. The traditional method of monitoring pilot flame assemblies is to install a thermocouple at the top of a flare stack and to run electrical leads from the thermocouple to a transmitter or other control system at grade. In case of problems with the thermocouple or with the pilot flame, a warning signal would typically alert operations personnel of the problem.
A problem with this traditional method is the fact that thermocouples routinely burn out and need replacing and, even with redundant or back-up thermocouples installed, there comes a time for change out. With the onset of new and more strictly-enforced environmental regulations, operating a plant when the thermocouples are disabled constitutes a violation of the regulations as given for example in the U.S. Code of Federal Regulations, Title 40, Part 60.18 a-f, unless another device capable of monitoring the flame, such as a remote optical sensor, is in place. Since a plant shutdown is therefore generally required to change out a thermocouple used in the traditional method, as it is unsafe to be in the vicinity of the flare without its being disabled, investments have been made in video equipment and the like which are aimed at the flare tip to detect the presence of a pilot flame. These units, however, are very costly to purchase and maintain.
Another problem associated with changing out thermocouples is one of time. Many state environmental agencies' regulations require that upon loss of pilot flame indication that visual verification that the pilot flame is lit has to be made every 15 minutes and recorded in a log book. If it takes more than 15 minutes to verify that the flare pilot flame is lit then the plant has to be shut down in order to correct the situation. If the problem lies with the thermocouple then it is of importance to effect a change within the 15 minute period, if the visual verification cannot be made.